A: One of the big draws of exchange-traded funds is their low fees. But that's not always the case.

A vast majority of ETFs have rock-bottom expense ratios, well below 1% for instance. The popular SPDR S&P 500 ETF, which allows investors to buy the stocks in the Standard & Poor's 500 index, has an annual expense ratio of 0.09%. But there are some shockingly high expense ratios on some ETFs for investors who look hard enough.

The ETF with the highest net expense ratio tracked by Morningstar is Market Vectors BDC Income, which trades by the symbol BIZD. Market Vectors BDC carries a lofty net expense ratio of 8.3%, which is shockingly high even compared to a mutual fund. The ETF invests in companies that are in the US Business Development Companies Index. Companies in this index are publicly traded, and they invest money in small companies or other companies in need of capital. The index owns stocks like Ares Capital, American Capital and Prospect Capital.

Following the Market Vector BDC in the high fee race is the Global X MLP ETF, which trades by the symbol MLPA. This ETF owns stocks that are in the Solactive MLP Composite index. MLPs, or master limited partnerships , are types of companies designed to generate large dividends by owning companies in stable industries. Don't let these high fees scare you from ETFs, though. Low fees are more the norm with ETFs and at some brokers you can also purchase ETFs without incurring commissions.